Scientists at the Lawrence Berkeley National Laboratory have developed a means of converting mechanical energy into electrical energy using a harmless, specially engineered virus. By simply tapping a finger on a virus-coated electrode the size of a postage stamp, the scientists were able to produce enough current to drive a liquid crystal display, albeit a very small one. The scientists claim that this is the first time that the piezoelectrical properties of a biological material have been harnessed.
To recap, piezoelectricity is the electrical charge that can build up in solid materials when they experience mechanical stress. It's a principle that could be put to use to harvest energy from common, everyday events like the fall of a shoe against a sidewalk, the closing of a door, or even typing with a notebook.
Because many of the piezoelectric materials in use today are toxic, the researchers wondered whether a particular virus known as M13, common to laboratories all over the world, might be piezoelectric. As the virus targets bacteria and is harmless to people, the scientists theorized that it might one day encourage more widespread use of piezoelectrics.
To determine whether the M13 bacteriophage was indeed piezoelectric, a film of the virus was exposed to an electrical field. When observed through a specialized microscope, helical proteins that coat rods of the virus were observed to move, confirming a piezoelectric effect.
The scientists found that they were able to further boost the charges induced in the virus by genetically engineering them with an extra four negatively charged amino acid residue at one end of these helical proteins.
An added benefit of using the virus, according to the scientists, is that that they self-arrange into the film that enables generation to take place, and by infecting bacteria, the virus can be made to reproduce, generating millions of copies over night. (This kind of self-arrangement and replication may one day prove handy for self-assembling nanotechnology, the scientists surmise). The charge was further boosted by stacking these virus films into layers, with a stack 20 layers thick demonstrating the strongest piezoelectric effect.
The system developed by the scientists had a potential difference of 400 millivolts, capable of generating an electrical current of six nanoamperes. A demo of the virus-powered LCD can be seen near the end of the video below.